Debra Audio AU400 4 channel wireless microphone system.(Two set frequncy point: A- 501/511.5/524/538.5 B-506/517.5/531/546.5) These series products adopt UHF frequency and use the international standard common frequency which can be used in all over the world. Due to the low frequency and many reasons, traditional wireless microphone usually disturbed by many factors especially by the variety of harmonic which send off by the CD/DVD/VCD/LD and other any digital equipments. Squelch circuit usually analysis the intensity of the RF frequency channel instead of the noise and the needed signal. Using the low traditional wireless microphone in the complex environment or when the signal of the microphone is week or the microphone is closed, the squelch circuit many suddenly opened which result the receiver send out a strong burst of noise. It ideal for church, small DJ KJ stage, birthday wedding or family party, conference, classrooms, small karaoke night etc. This product comes in black, is handheld, and uses an AUX/XLR connector type. Packing list: Wireless Receiver*1, Handheld Microphone*2, Bodypack Receiver (with Headphones)*2, Audio cable*1, Power supply*1, Manual*1